From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1URbQB-0000QS-CL for kexec@lists.infradead.org; Mon, 15 Apr 2013 04:53:40 +0000 Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id E19523EE0C0 for ; Mon, 15 Apr 2013 13:53:26 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id C291A45DDCF for ; Mon, 15 Apr 2013 13:53:26 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id A45E745DE55 for ; Mon, 15 Apr 2013 13:53:26 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 7992E1DB8047 for ; Mon, 15 Apr 2013 13:53:26 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.240.81.134]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id C003CE0800F for ; Mon, 15 Apr 2013 13:53:25 +0900 (JST) Message-ID: <516B87A6.9080708@jp.fujitsu.com> Date: Mon, 15 Apr 2013 13:52:54 +0900 From: HATAYAMA Daisuke MIME-Version: 1.0 Subject: Re: [PATCH 5/5] kexec: X86: Pass memory ranges via e820 table instead of memmap= boot parameter References: <1365683207-42425-1-git-send-email-trenn@suse.de> <1365683207-42425-6-git-send-email-trenn@suse.de> <5166D18A.7090800@zytor.com> <20130412143104.GA4301@redhat.com> <5168208B.7050107@zytor.com> <51688803.8020401@sr71.net> In-Reply-To: <51688803.8020401@sr71.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: Dave Hansen Cc: "kexec@lists.infradead.org" , Linux Kernel Mailing List , Thomas Renninger , Simon Horman , "Eric W. Biederman" , "H. Peter Anvin" , Yinghai Lu , Cliff Wickman , Vivek Goyal (2013/04/13 7:17), Dave Hansen wrote: > On 04/12/2013 07:56 AM, H. Peter Anvin wrote: >> On 04/12/2013 07:31 AM, Vivek Goyal wrote: >>>> I also have to admit that I don't see the difference between /dev/mem >>>> and /dev/oldmem, as the former allows access to memory ranges outside >>>> the ones used by the current kernel, which is what the oldmem device >>>> seems to be intended to od. > > It varies from arch to arch of course. > > But, /dev/mem has restrictions on it, like CONFIG_STRICT_DEVMEM or the > ARCH_HAS_VALID_PHYS_ADDR_RANGE. There's a lot of stuff that depends on > it, *and* folks have tried to fix it up so that it's not _as_ blatant of > a way to completely screw your system. > > /dev/mem also tries to be nice to arches that have restrictions like: > >> /* >> * On ia64 if a page has been mapped somewhere as >> * uncached, then it must also be accessed uncached >> * by the kernel or data corruption may occur >> */ > > I think /dev/oldmem isn't so nice and could actually cause some real > problems if used on ia64 where the cached/uncached accesses are mixed. This sounds like there's no such issue on x86 cache mechanism. Is it correct? If so, what is the difference between ia64 and x86 cache mechanisms? -- Thanks. HATAYAMA, Daisuke _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec